The present invention relates to a method for mounting electronic components on an insulating layer, an electronic component-embedded substrate, and a method for manufacturing the electronic component-embedded substrate.
In general, a substrate (an electronic component-embedded substrate) on which electronic components such as semiconductor devices (an IC and another semiconductor active device) are mounted has a structure in which the semiconductor devices (dies) having a bare chip state are fixed to the substrate including a single resin layer or a plurality of resin layers, and to meet demands for high performance and miniaturization of an electronic device, development of a module has been advanced on which active components such as the semiconductor devices and passive components such as resistances and capacitors are highly densely mounted.
In recent years, with regard to portable devices typified by a portable terminal such as a cellular phone, mounting with a density much higher than every before has earnestly been demanded, and these days, especially a demand for thinning has risen. On the other hand, also with regard to the electronic component-embedded substrate for use in such a portable device, higher densification and thinning are earnestly demanded, and further thinning of the electronic components themselves also rapidly advances.
In such manufacturing steps of the electronic component-embedded substrate, in general, after bonding and fixing a semiconductor device to an insulating layer such as the resin layer or an insulating base, land electrodes of the semiconductor device are connected to an internal wiring pattern in the electronic component-embedded substrate by wire bonding or flip chip connection. It is described in, for example, Japanese Patent Application Laid-Open No. 8-88316 that a semiconductor bare chip is bonded onto the substrate with an adhesive and that the semiconductor bare chip is connected to a wiring layer by wire bonding. A method is also known in which the semiconductor device is disposed on an unhardened resin layer, and the resin layer is hardened to fix both the device and the layer.
In addition, in a case where the semiconductor device is mounted on the substrate as described above, in order to firmly secure the semiconductor device to the insulating layer, the base or the like, the semiconductor device is tentatively set on the adhesive or the unhardened resin layer, and then pressed to come in close contact with the adhesive and the layer (pressed), and in this state, the adhesive and the resin layer need to be hardened. In this case, a method is used in which, for example, a ceramic-made grasping tool (e.g., a jig such as a collet for use in a die bonder unit) is usually attached to one surface of the semiconductor device to hold the semiconductor device by adsorption or the like, an opposite surface of the semiconductor device in this state is allowed to abut on the resin layer or the like and tentatively set, and further the pressure is applied to the semiconductor device with the grasping tool to attach and press the device to the resin layer or the like.
However, as described above, in recent years, the semiconductor device itself has become very thin (e.g., a several ten μm order). According to findings of the present inventor, it has been found that in a case where such a thin semiconductor device is physically pressed with a jig, even when it is intended to uniformly press the semiconductor device, a pressure is concentrated on a peripheral edge portion of the semiconductor device, and warp and bend tend to be unavoidably generated in the semiconductor device in which the resin layer or the like has been hardened. Moreover, in a case where, as described in Japanese Patent Application Laid-Open No. 8-88316, the surface of the semiconductor device on which any land electrode or bump is not formed is installed so as to face a resin layer side (a so-called face-up system), the surface on which the land electrodes and the bumps are formed needs to be grasped and pressed. Therefore, in a case where the semiconductor device is grasped and pressed so as to avoid the land electrodes and the bumps so that they are not damaged, the pressure to be applied to the semiconductor device is further locally and unevenly distributed, and the warp and the bend of the semiconductor device might become further conspicuous.
When the semiconductor device warps and bends in this manner, positions (especially positions in a height direction) of the land electrodes and the bumps deviate. Therefore, it might be difficult to securely connect the semiconductor device to the wiring layer, and deterioration of reliability of the electronic component-embedded substrate and deterioration of yield of a product might be caused. Moreover, in an electronic component-embedded substrate having a multilayered structure, multiple stages of resin layers and wiring layers are provided on the semiconductor device fixed to the substrate. Therefore, to securely connect these components, there is an increasingly strict restriction on an installing dimension of the semiconductor device, and a problem that the semiconductor device warps and bends is especially serious.
Moreover, when the semiconductor device is pressed onto the resin layer or the like, the device tends to warp and bend so that the peripheral edge portion of the device sinks in (caves in) the resin layer or the like. In this case, the resin in the vicinity of the peripheral edge portion of the semiconductor device easily rises at a peripheral wall of the device. According to the findings of the present inventor, a portion of the unhardened resin layer raised on the “side” of the semiconductor device in this manner easily becomes porous. In this case, a disadvantage occurs that even after the resin layer hardens, a fixing strength between the peripheral edge portion of the semiconductor device and the resin layer and a transverse strength of the substrate itself deteriorate, and a void portion of the resin layer easily absorbs humidity.
The above-mentioned situation similarly applies to electronic components other than the semiconductor device to be mounted on the substrate or the like.